The monitoring of individual parking positions in in-door car parks or public traffic spaces presently uses cable-linked sensors for vehicle detection, the common practice being the use of ultrasonic, infrared or geomagnetic field sensors. Optical indication is effected by cable-linked lights or light emitting diodes as well. The cable links are needed because of the high energy consumption of the sensors and the optical indicator elements. Likewise, cables are used for transmitting occupied/free data relating to each parking position to a network connected to the parking facility control center. The cabling of the prior individual parking position monitoring devices necessitates considerable capital outlays especially if retrofitted. The cost of laying the cables may far exceed that of the sensors and the optical indicators themselves.